1. Field of the Invention
The present invention relates to an optical network system that is able to support different transmission speeds for an optical base station apparatus and an optical subscriber terminal in a time division multiple access (TDMA) passive optical network (PON) system.
2. Description of the Related Art
Among Fiber to the Home (FTTH) access methods that are widely applied, a passive optical network (PON) configured with passive elements boasts a widespread usage due to cost effectiveness and convenient maintenance.
In a time division system PON, a PON uses a method of transmitting data of a subscriber end by assigning the data of the subscriber end to a time slot, and may be classified into an Ethernet passive optical network (EPON) and a Gigabit passive optical network (G-PON) based on a protocol structure.
The EPON standard of the Institute of Electrical and Electronics Engineers (IEEE), an international standardization organization, has a transmission speed of 1.25 gigabits per second (Gbps) downstream and 1.25 Gbps upstream. The G-PON standard of the International Telecommunication Union, Telecommunication Standardization Sector (ITU-T) has the transmission speed of 2.5 Gbps downstream and 1.25 Gbps upstream.
Due to a growing demand for a high density Internet Protocol Television (IPTV), a next generation subscriber end service, and the like, research is being conducted to increase the transmission speed of the EPON and the G-PON that generally operate at a transmission speed in the range of Gbps.
One of the primary aspects of a next generation 10 Gbps PON is that an asymmetric configuration in which a downstream transmission speed and an upstream transmission speed differ may be adopted simultaneously with a symmetric configuration.
Transitively, in a system in which the symmetric configuration and the asymmetric configuration are separated, cost effectiveness of a current service may be achieved. Moreover, the asymmetric configuration may have a configuration in which only a downstream receiving data has a transmission speed of 10 Gbps by using an aspect of having more service reception bandwidths than transmission bandwidths.
In this instance, an interface between a physical layer (PHY) block and a media access control (MAC) block with respect to an upstream optical signal has an intricate configuration, and applying the configuration to a system may be difficult.
Since a 10 Gbps XG-PON standard uses an identical wavelength of the asymmetric configuration and the symmetric configuration, when the asymmetric configuration and the symmetric configuration coexist, it may be costly due to a need to change an entire system.
Accordingly, in a case of the asymmetric configuration and the symmetric configuration coexisting with respect to an optical network system, there is a need for a simple system configuration.